RFR: Add "verify jcstress" acceptance test

[Aleksey Shipilev]

Hi,

Recent bug in shenandoah/8u had slipped under the radar, because we don't have
any test that runs with -XX:+ShenandoahVerifyOptoBarriers included into
hotspot_gc_shenandoah.

Add one:
  http://cr.openjdk.java.net/~shade/shenandoah/tests-verify-jcstress/webrev.01/

This goes to 10, 9, 8u.

Testing: hotspot_gc_shenandoah

Checked it fails with a few obvious injected bugs in compiler (reverting
arraycopy verification fix), in runtime (e.g. using == instead of
oopDesc::equals), etc.

Thanks,
-Aleksey